this is my Dad and his team mates of PT Instructors practicing onboard ship, (Royal Navy) in the 1930's.

My Dad is at the far left end of the parallel bars, performing the "hand stand", altho that is not the name of the stunt : ) (wish he was here so that I could ask him the correct name : )

Realize the image is not straight, but that is due to the ship's motion, - so adds to the "feeling" and authenticity, right.

Can you imagine how difficult it would be to perform this type of gymnastic stunt, on a rolling ship LOL